diff --git a/metropolis/pkg/event/etcd/BUILD.bazel b/metropolis/pkg/event/etcd/BUILD.bazel
new file mode 100644
index 0000000..b00bc47
--- /dev/null
+++ b/metropolis/pkg/event/etcd/BUILD.bazel
@@ -0,0 +1,28 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["etcd.go"],
+    importpath = "source.monogon.dev/metropolis/pkg/event/etcd",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//metropolis/node/core/consensus/client:go_default_library",
+        "//metropolis/pkg/event:go_default_library",
+        "@com_github_cenkalti_backoff_v4//:go_default_library",
+        "@io_etcd_go_etcd//clientv3:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["etcd_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//metropolis/node/core/consensus/client:go_default_library",
+        "//metropolis/pkg/event:go_default_library",
+        "@io_etcd_go_etcd//clientv3:go_default_library",
+        "@io_etcd_go_etcd//etcdserver/api/v3rpc/rpctypes:go_default_library",
+        "@io_etcd_go_etcd//integration:go_default_library",
+        "@org_golang_google_grpc//codes:go_default_library",
+    ],
+)
diff --git a/metropolis/pkg/event/etcd/etcd.go b/metropolis/pkg/event/etcd/etcd.go
new file mode 100644
index 0000000..041e600
--- /dev/null
+++ b/metropolis/pkg/event/etcd/etcd.go
@@ -0,0 +1,258 @@
+package etcd
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+
+	"github.com/cenkalti/backoff/v4"
+	"go.etcd.io/etcd/clientv3"
+
+	"source.monogon.dev/metropolis/node/core/consensus/client"
+	"source.monogon.dev/metropolis/pkg/event"
+)
+
+var (
+	// Type assert that *Value implements event.Value. We do this artificially,
+	// as there currently is no code path that needs this to be strictly true.
+	// However, users of this library might want to rely on the Value type
+	// instead of particular Value implementations.
+	_ event.Value = &Value{}
+)
+
+// Value is an 'Event Value' backed in an etcd cluster, accessed over an
+// etcd client. This is a stateless handle and can be copied and shared across
+// goroutines.
+type Value struct {
+	etcd    client.Namespaced
+	key     string
+	decoder BytesDecoder
+}
+
+// NewValue creates a new Value for a given key in an etcd client. The
+// given decoder will be used to convert bytes retrieved from etcd into the
+// interface{} value retrieved by Get by this value's watcher.
+func NewValue(etcd client.Namespaced, key string, decoder BytesDecoder) *Value {
+	return &Value{
+		etcd:    etcd,
+		key:     key,
+		decoder: decoder,
+	}
+}
+
+// BytesDecoder is a function that converts bytes retrieved from etcd into an
+// end-user facing value. If an error is returned, the Get call performed on a
+// watcher configured with this decoder will fail, swallowing that particular
+// update, but the watcher will continue to work.
+// Any provided BytesDecoder implementations must be safe to copy.
+type BytesDecoder = func(data []byte) (interface{}, error)
+
+// NoDecoder is a no-op decoder which passes through the retrieved bytes as a
+// []byte type to the user.
+func NoDecoder(data []byte) (interface{}, error) {
+	return data, nil
+}
+
+func (e *Value) Set(val interface{}) {
+	// TODO(q3k): split up the Value interface into ValueReader/ValueWriter
+	panic("Set is unimplemented on etcd values")
+}
+
+func (e *Value) Watch() event.Watcher {
+	ctx, ctxC := context.WithCancel(context.Background())
+	return &watcher{
+		Value: *e,
+
+		ctx:  ctx,
+		ctxC: ctxC,
+
+		getSem: make(chan struct{}, 1),
+	}
+}
+
+type watcher struct {
+	// Value copy, used to configure the behaviour of this watcher.
+	Value
+
+	// ctx is the context that expresses the liveness of this watcher. It is
+	// canceled when the watcher is closed, and the etcd Watch hangs off of it.
+	ctx  context.Context
+	ctxC context.CancelFunc
+
+	// getSem is a semaphore used to limit concurrent Get calls and throw an
+	// error if concurrent access is attempted.
+	getSem chan struct{}
+
+	// backlogged is the value retrieved by an initial KV Get from etcd that
+	// should be returned at the next opportunity, or nil if there isn't any.
+	backlogged *[]byte
+	// prev is the revision of a previously retrieved value within this
+	// watcher, or nil if there hasn't been any.
+	prev *int64
+	// wc is the etcd watch channel, or nil if no channel is yet open.
+	wc clientv3.WatchChan
+
+	// testRaceWG is an optional WaitGroup that, if set, will be waited upon
+	// after the initial KV value retrieval, but before the watch is created.
+	// This is only used for testing.
+	testRaceWG *sync.WaitGroup
+	// testSetupWG is an optional WaitGroup that, if set, will be waited upon
+	// after the etcd watch is created.
+	// This is only used for testing.
+	testSetupWG *sync.WaitGroup
+}
+
+func (w *watcher) setup(ctx context.Context) error {
+	if w.wc != nil {
+		return nil
+	}
+
+	// First, check if some data under this key already exists.
+	// We use an exponential backoff and retry here as the initial Get can fail
+	// if the cluster is unstable (eg. failing over). We only fail the retry if
+	// the context expires.
+	bo := backoff.NewExponentialBackOff()
+	bo.MaxElapsedTime = 0
+	err := backoff.Retry(func() error {
+		get, err := w.etcd.Get(ctx, w.key)
+		if err != nil {
+			return fmt.Errorf("when retrieving initial value: %w", err)
+		}
+		w.prev = &get.Header.Revision
+		if len(get.Kvs) != 0 {
+			// Assert that the etcd API is behaving as expected.
+			if len(get.Kvs) > 1 {
+				panic("More than one key returned in unary GET response")
+			}
+			// If an existing value is present, backlog it and set the prev value
+			// accordingly.
+			kv := get.Kvs[0]
+			w.backlogged = &kv.Value
+		} else {
+			w.backlogged = nil
+		}
+		return nil
+
+	}, backoff.WithContext(bo, ctx))
+
+	if w.testRaceWG != nil {
+		w.testRaceWG.Wait()
+	}
+	if err != nil {
+		return err
+	}
+
+	var watchOpts []clientv3.OpOption
+	if w.prev != nil {
+		watchOpts = append(watchOpts, clientv3.WithRev(*w.prev+1))
+	} else {
+	}
+	w.wc = w.etcd.Watch(w.ctx, w.key, watchOpts...)
+
+	if w.testSetupWG != nil {
+		w.testSetupWG.Wait()
+	}
+	return nil
+}
+
+func (w *watcher) get(ctx context.Context) ([]byte, error) {
+	// Return backlogged value, if present.
+	if w.backlogged != nil {
+		value := *w.backlogged
+		w.backlogged = nil
+		return value, nil
+	}
+
+	// Keep watching for a watch event.
+	var event *clientv3.Event
+	for {
+		var resp *clientv3.WatchResponse
+		select {
+		case r := <-w.wc:
+			resp = &r
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		}
+
+		if resp.Canceled {
+			// Only allow for watches to be canceled due to context
+			// cancellations. Any other error is something we need to handle,
+			// eg. a client close or compaction error.
+			if errors.Is(resp.Err(), ctx.Err()) {
+				return nil, fmt.Errorf("watch canceled: %w", resp.Err())
+			}
+
+			// Attempt to reconnect.
+			w.wc = nil
+			w.setup(ctx)
+			continue
+		}
+
+		if len(resp.Events) < 1 {
+			continue
+		}
+
+		event = resp.Events[len(resp.Events)-1]
+		break
+	}
+
+	w.prev = &event.Kv.ModRevision
+	// Return deletions as nil, and new values as their content.
+	switch event.Type {
+	case clientv3.EventTypeDelete:
+		return nil, nil
+	case clientv3.EventTypePut:
+		return event.Kv.Value, nil
+	default:
+		return nil, fmt.Errorf("invalid event type %v", event.Type)
+	}
+}
+
+// Get implements the Get method of the Watcher interface.
+// It can return an error in two cases:
+//  - the given context is canceled (in which case, the given error will wrap
+//    the context error)
+//  - the watcher's BytesDecoder returned an error (in which case the error
+//    returned by the BytesDecoder will be returned verbatim)
+// Note that transient and permanent etcd errors are never returned, and the
+// Get call will attempt to recover from these errors as much as possible. This
+// also means that the user of the Watcher will not be notified if the
+// underlying etcd client disconnects from the cluster, or if the cluster loses
+// quorum.
+// TODO(q3k): implement leases to allow clients to be notified when there are
+// transient cluster/quorum/partition errors, if needed.
+// TODO(q3k): implement internal, limited buffering for backlogged data not yet
+// consumed by client, as etcd client library seems to use an unbound buffer in
+// case this happens ( see: watcherStream.buf in clientv3).
+func (w *watcher) Get(ctx context.Context) (interface{}, error) {
+	select {
+	case w.getSem <- struct{}{}:
+	default:
+		return nil, fmt.Errorf("cannot Get() concurrently on a single waiter")
+	}
+	defer func() {
+		<-w.getSem
+	}()
+
+	// Early check for context cancelations, preventing spurious contact with etcd
+	// if there's no need to.
+	if w.ctx.Err() != nil {
+		return nil, w.ctx.Err()
+	}
+
+	if err := w.setup(ctx); err != nil {
+		return nil, fmt.Errorf("when setting up watcher: %w", err)
+	}
+
+	value, err := w.get(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("when watching for new value: %w", err)
+	}
+	return w.decoder(value)
+}
+
+func (w *watcher) Close() error {
+	w.ctxC()
+	return nil
+}
diff --git a/metropolis/pkg/event/etcd/etcd_test.go b/metropolis/pkg/event/etcd/etcd_test.go
new file mode 100644
index 0000000..79d9875
--- /dev/null
+++ b/metropolis/pkg/event/etcd/etcd_test.go
@@ -0,0 +1,584 @@
+package etcd
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"sync"
+	"testing"
+	"time"
+
+	"go.etcd.io/etcd/clientv3"
+	"go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
+	"go.etcd.io/etcd/integration"
+	"google.golang.org/grpc/codes"
+
+	"source.monogon.dev/metropolis/node/core/consensus/client"
+	"source.monogon.dev/metropolis/pkg/event"
+)
+
+var (
+	cluster   *integration.ClusterV3
+	endpoints []string
+)
+
+// TestMain brings up a 3 node etcd cluster for tests to use.
+func TestMain(m *testing.M) {
+	cfg := integration.ClusterConfig{
+		Size:                 3,
+		GRPCKeepAliveMinTime: time.Millisecond,
+	}
+	cluster = integration.NewClusterV3(nil, &cfg)
+	endpoints = make([]string, 3)
+	for i := range endpoints {
+		endpoints[i] = cluster.Client(i).Endpoints()[0]
+	}
+
+	v := m.Run()
+	cluster.Terminate(nil)
+	os.Exit(v)
+}
+
+// setRaceWg creates a new WaitGroup and sets the given watcher to wait on this
+// WG after it performs the initial retrieval of a value from etcd, but before
+// it starts the watcher. This is used to test potential race conditions
+// present between these two steps.
+func setRaceWg(w event.Watcher) *sync.WaitGroup {
+	wg := sync.WaitGroup{}
+	w.(*watcher).testRaceWG = &wg
+	return &wg
+}
+
+// setSetupWg creates a new WaitGroup and sets the given watcher to wait on
+// thie WG after an etcd watch channel is created. This is used in tests to
+// ensure that the watcher is fully created before it is tested.
+func setSetupWg(w event.Watcher) *sync.WaitGroup {
+	wg := sync.WaitGroup{}
+	w.(*watcher).testSetupWG = &wg
+	return &wg
+}
+
+// testClient is an etcd connection to the test cluster.
+type testClient struct {
+	client     *clientv3.Client
+	namespaced client.Namespaced
+}
+
+func newTestClient(t *testing.T) *testClient {
+	t.Helper()
+	cli, err := clientv3.New(clientv3.Config{
+		Endpoints:            endpoints,
+		DialTimeout:          1 * time.Second,
+		DialKeepAliveTime:    1 * time.Second,
+		DialKeepAliveTimeout: 1 * time.Second,
+	})
+	if err != nil {
+		t.Fatalf("clientv3.New: %v", err)
+	}
+
+	namespaced := client.NewLocal(cli)
+	return &testClient{
+		client:     cli,
+		namespaced: namespaced,
+	}
+}
+
+func (d *testClient) close() {
+	d.client.Close()
+}
+
+// setEndpoints configures which endpoints (from {0,1,2}) the testClient is
+// connected to.
+func (d *testClient) setEndpoints(nums ...uint) {
+	var eps []string
+	for _, num := range nums {
+		eps = append(eps, endpoints[num])
+	}
+	d.client.SetEndpoints(eps...)
+}
+
+// put uses the testClient to store key with a given string value in etcd. It
+// contains retry logic that will block until the put is successful.
+func (d *testClient) put(t *testing.T, key, value string) {
+	t.Helper()
+	ctx, ctxC := context.WithCancel(context.Background())
+	defer ctxC()
+
+	for {
+		ctxT, ctxC := context.WithTimeout(ctx, 100*time.Millisecond)
+		_, err := d.namespaced.Put(ctxT, key, value)
+		ctxC()
+		if err == nil {
+			return
+		}
+		if err == ctxT.Err() {
+			log.Printf("Retrying after %v", err)
+			continue
+		}
+		// Retry on etcd unavailability - this will happen in this code as the
+		// etcd cluster repeatedly loses quorum.
+		var eerr rpctypes.EtcdError
+		if errors.As(err, &eerr) && eerr.Code() == codes.Unavailable {
+			log.Printf("Retrying after %v", err)
+			continue
+		}
+		t.Fatalf("Put: %v", err)
+	}
+
+}
+
+// remove uses the testClient to remove the given key from etcd. It contains
+// retry logic that will block until the removal is successful.
+func (d *testClient) remove(t *testing.T, key string) {
+	t.Helper()
+	ctx, ctxC := context.WithCancel(context.Background())
+	defer ctxC()
+
+	_, err := d.namespaced.Delete(ctx, key)
+	if err == nil {
+		return
+	}
+	t.Fatalf("Delete: %v", err)
+}
+
+// expect runs a Get on the given Watcher, ensuring the returned value is a
+// given string.
+func expect(t *testing.T, w event.Watcher, value string) {
+	t.Helper()
+	ctx, ctxC := context.WithCancel(context.Background())
+	defer ctxC()
+
+	got, err := w.Get(ctx)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+
+	if got, want := string(got.([]byte)), value; got != want {
+		t.Errorf("Got value %q, wanted %q", want, got)
+	}
+}
+
+// expectTimeout ensures that the given watcher blocks on a Get call for at
+// least 100 milliseconds. This is used by tests to attempt to verify that the
+// watcher Get is fully blocked, but can cause false positives (eg. when Get
+// blocks for 101 milliseconds). Thus, this function should be used sparingly
+// and in tests that perform other baseline behaviour checks alongside this
+// test.
+func expectTimeout(t *testing.T, w event.Watcher) {
+	t.Helper()
+	ctx, ctxC := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	got, err := w.Get(ctx)
+	ctxC()
+
+	if !errors.Is(err, ctx.Err()) {
+		t.Fatalf("Expected timeout error, got %v, %v", got, err)
+	}
+}
+
+// wait wraps a watcher into a channel of strings, ensuring that the watcher
+// never errors on Get calls and always returns strings.
+func wait(t *testing.T, w event.Watcher) (chan string, func()) {
+	t.Helper()
+	ctx, ctxC := context.WithCancel(context.Background())
+
+	c := make(chan string)
+
+	go func() {
+		for {
+			got, err := w.Get(ctx)
+			if err != nil && errors.Is(err, ctx.Err()) {
+				return
+			}
+			if err != nil {
+				t.Fatalf("Get: %v", err)
+			}
+			c <- string(got.([]byte))
+		}
+	}()
+
+	return c, ctxC
+}
+
+// TestSimple exercises the simplest possible interaction with a watched value.
+func TestSimple(t *testing.T) {
+	tc := newTestClient(t)
+	defer tc.close()
+
+	k := "test-simple"
+	value := NewValue(tc.namespaced, k, NoDecoder)
+	tc.put(t, k, "one")
+
+	watcher := value.Watch()
+	defer watcher.Close()
+	expect(t, watcher, "one")
+
+	tc.put(t, k, "two")
+	expect(t, watcher, "two")
+
+	tc.put(t, k, "three")
+	tc.put(t, k, "four")
+	tc.put(t, k, "five")
+	tc.put(t, k, "six")
+
+	q, cancel := wait(t, watcher)
+	// Test will hang here if the above value does not receive the set "six".
+	for el := range q {
+		if el == "six" {
+			break
+		}
+	}
+	cancel()
+}
+
+// TestCancel ensures that watchers can resume after being canceled.
+func TestCancel(t *testing.T) {
+	tc := newTestClient(t)
+	defer tc.close()
+
+	k := "test-cancel"
+	value := NewValue(tc.namespaced, k, NoDecoder)
+	tc.put(t, k, "one")
+
+	watcher := value.Watch()
+	defer watcher.Close()
+	expect(t, watcher, "one")
+
+	ctx, ctxC := context.WithCancel(context.Background())
+	errs := make(chan error, 1)
+	go func() {
+		_, err := watcher.Get(ctx)
+		errs <- err
+	}()
+	ctxC()
+	if want, got := ctx.Err(), <-errs; !errors.Is(got, want) {
+		t.Fatalf("Wanted err %v, got %v", want, got)
+	}
+
+	// Successfully canceled watch, resuming should continue to work.
+	q, cancel := wait(t, watcher)
+	defer cancel()
+
+	tc.put(t, k, "two")
+	if want, got := "two", <-q; want != got {
+		t.Fatalf("Wanted val %q, got %q", want, got)
+	}
+}
+
+// TestCancelOnGet ensures that a context cancellation on an initial Get (which
+// translates to an etcd Get in a backoff loop) doesn't block.
+func TestCancelOnGet(t *testing.T) {
+	tc := newTestClient(t)
+	defer tc.close()
+
+	k := "test-cancel-on-get"
+	value := NewValue(tc.namespaced, k, NoDecoder)
+	watcher := value.Watch()
+	tc.put(t, k, "one")
+
+	// Cause partition between client endpoint and rest of cluster. Any read/write
+	// operations will now hang.
+	tc.setEndpoints(0)
+	cluster.Members[0].InjectPartition(t, cluster.Members[1], cluster.Members[2])
+
+	// Perform the initial Get(), which should attempt to retrieve a KV entry from
+	// the etcd service. This should hang. Unfortunately, there's no easy way to do
+	// this without an arbitrary sleep hoping that the client actually gets to the
+	// underlying etcd.Get call. This can cause false positives (eg. false 'pass'
+	// results) in this test.
+	ctx, ctxC := context.WithCancel(context.Background())
+	errs := make(chan error, 1)
+	go func() {
+		_, err := watcher.Get(ctx)
+		errs <- err
+	}()
+	time.Sleep(time.Second)
+
+	// Now that the etcd.Get is hanging, cancel the context.
+	ctxC()
+	// And now unpartition the cluster, resuming reads.
+	cluster.Members[0].RecoverPartition(t, cluster.Members[1], cluster.Members[2])
+
+	// The etcd.Get() call should've returned with a context cancellation.
+	err := <-errs
+	switch {
+	case err == nil:
+		t.Errorf("watcher.Get() returned no error, wanted context error")
+	case errors.Is(err, ctx.Err()):
+		// Okay.
+	default:
+		t.Errorf("watcher.Get() returned %v, wanted context error", err)
+	}
+}
+
+// TestClientReconnect forces a 'reconnection' of an active watcher from a
+// running member to another member, by stopping the original member and
+// explicitly reconnecting the client to other available members.
+//
+// This doe not reflect a situation expected during Metropolis runtime, as we
+// do not expect splits between an etcd client and its connected member
+// (instead, all etcd clients only connect to their local member). However, it
+// is still an important safety test to perform, and it also exercies the
+// equivalent behaviour of an etcd client re-connecting for any other reason.
+func TestClientReconnect(t *testing.T) {
+	tc := newTestClient(t)
+	defer tc.close()
+	tc.setEndpoints(0)
+
+	k := "test-client-reconnect"
+	value := NewValue(tc.namespaced, k, NoDecoder)
+	tc.put(t, k, "one")
+
+	watcher := value.Watch()
+	defer watcher.Close()
+	expect(t, watcher, "one")
+
+	q, cancel := wait(t, watcher)
+	defer cancel()
+
+	cluster.Members[0].Stop(t)
+	defer cluster.Members[0].Restart(t)
+	cluster.WaitLeader(t)
+
+	tc.setEndpoints(1, 2)
+	tc.put(t, k, "two")
+
+	if want, got := "two", <-q; want != got {
+		t.Fatalf("Watcher received incorrect data after client restart, wanted %q, got %q", want, got)
+	}
+}
+
+// TestClientPartition forces a temporary partition of the etcd member while a
+// watcher is running, updates the value from across the partition, and undoes
+// the partition.
+// The partition is expected to be entirely transparent to the watcher.
+func TestClientPartition(t *testing.T) {
+	tcOne := newTestClient(t)
+	defer tcOne.close()
+	tcOne.setEndpoints(0)
+
+	tcRest := newTestClient(t)
+	defer tcRest.close()
+	tcRest.setEndpoints(1, 2)
+
+	k := "test-client-partition"
+	valueOne := NewValue(tcOne.namespaced, k, NoDecoder)
+	watcherOne := valueOne.Watch()
+	defer watcherOne.Close()
+	valueRest := NewValue(tcRest.namespaced, k, NoDecoder)
+	watcherRest := valueRest.Watch()
+	defer watcherRest.Close()
+
+	tcRest.put(t, k, "a")
+	expect(t, watcherOne, "a")
+	expect(t, watcherRest, "a")
+
+	cluster.Members[0].InjectPartition(t, cluster.Members[1], cluster.Members[2])
+
+	tcRest.put(t, k, "b")
+	expect(t, watcherRest, "b")
+	expectTimeout(t, watcherOne)
+
+	cluster.Members[0].RecoverPartition(t, cluster.Members[1], cluster.Members[2])
+
+	expect(t, watcherOne, "b")
+	tcRest.put(t, k, "c")
+	expect(t, watcherOne, "c")
+	expect(t, watcherRest, "c")
+
+}
+
+// TestEarlyUse exercises the correct behaviour of the value watcher on a value
+// that is not yet set.
+func TestEarlyUse(t *testing.T) {
+	tc := newTestClient(t)
+	defer tc.close()
+
+	k := "test-early-use"
+
+	value := NewValue(tc.namespaced, k, NoDecoder)
+	watcher := value.Watch()
+	defer watcher.Close()
+
+	wg := setSetupWg(watcher)
+	wg.Add(1)
+	q, cancel := wait(t, watcher)
+	defer cancel()
+
+	wg.Done()
+
+	tc.put(t, k, "one")
+
+	if want, got := "one", <-q; want != got {
+		t.Fatalf("Expected %q, got %q", want, got)
+	}
+}
+
+// TestRemove exercises the basic functionality of handling deleted values.
+func TestRemove(t *testing.T) {
+	tc := newTestClient(t)
+	defer tc.close()
+
+	k := "test-remove"
+	tc.put(t, k, "one")
+
+	value := NewValue(tc.namespaced, k, NoDecoder)
+	watcher := value.Watch()
+	defer watcher.Close()
+
+	expect(t, watcher, "one")
+	tc.remove(t, k)
+	expect(t, watcher, "")
+}
+
+// TestEmptyRace forces the watcher to retrieve an empty value from the K/V
+// store at first, and establishing the watch channel after a new value has
+// been stored in the same place.
+func TestEmptyRace(t *testing.T) {
+	tc := newTestClient(t)
+	defer tc.close()
+
+	k := "test-remove-race"
+	tc.put(t, k, "one")
+	tc.remove(t, k)
+
+	value := NewValue(tc.namespaced, k, NoDecoder)
+	watcher := value.Watch()
+	defer watcher.Close()
+
+	wg := setRaceWg(watcher)
+	wg.Add(1)
+	q, cancel := wait(t, watcher)
+	defer cancel()
+
+	tc.put(t, k, "two")
+	wg.Done()
+
+	if want, got := "two", <-q; want != got {
+		t.Fatalf("Watcher received incorrect data after client restart, wanted %q, got %q", want, got)
+	}
+}
+
+type errOrInt struct {
+	val int64
+	err error
+}
+
+// TestDecoder exercises the BytesDecoder functionality of the watcher, by
+// creating a value with a decoder that only accepts string-encoded integers
+// that are divisible by three. The test then proceeds to put a handful of
+// values into etcd, ensuring that undecodable values correctly return an error
+// on Get, but that the watcher continues to work after the error has been
+// returned.
+func TestDecoder(t *testing.T) {
+	decodeStringifiedNumbersDivisibleBy3 := func(data []byte) (interface{}, error) {
+		num, err := strconv.ParseInt(string(data), 10, 64)
+		if err != nil {
+			return nil, fmt.Errorf("not a valid number")
+		}
+		if (num % 3) != 0 {
+			return nil, fmt.Errorf("not divisible by 3")
+		}
+		return num, nil
+	}
+
+	tc := newTestClient(t)
+	defer tc.close()
+
+	ctx, ctxC := context.WithCancel(context.Background())
+	defer ctxC()
+
+	k := "test-decoder"
+	value := NewValue(tc.namespaced, k, decodeStringifiedNumbersDivisibleBy3)
+	watcher := value.Watch()
+	defer watcher.Close()
+	tc.put(t, k, "3")
+	_, err := watcher.Get(ctx)
+	if err != nil {
+		t.Fatalf("Initial Get: %v", err)
+	}
+
+	// Stream updates into arbitrarily-bounded test channel.
+	queue := make(chan errOrInt, 100)
+	go func() {
+		for {
+			res, err := watcher.Get(ctx)
+			if err != nil && errors.Is(err, ctx.Err()) {
+				return
+			}
+			if err != nil {
+				queue <- errOrInt{
+					err: err,
+				}
+			} else {
+				queue <- errOrInt{
+					val: res.(int64),
+				}
+			}
+		}
+	}()
+
+	var wantList []*int64
+	wantError := func(val string) {
+		wantList = append(wantList, nil)
+		tc.put(t, k, val)
+	}
+	wantValue := func(val string, decoded int64) {
+		wantList = append(wantList, &decoded)
+		tc.put(t, k, val)
+	}
+
+	wantError("")
+	wantValue("9", 9)
+	wantError("foo")
+	wantValue("18", 18)
+	wantError("10")
+	wantError("10")
+	wantValue("27", 27)
+	wantValue("36", 36)
+
+	for i, want := range wantList {
+		q := <-queue
+		if want == nil && q.err == nil {
+			t.Errorf("Case %d: wanted error, got no error and value %d", i, q.val)
+		}
+		if want != nil && (*want) != q.val {
+			t.Errorf("Case %d: wanted value %d, got error %v and value %d", i, *want, q.err, q.val)
+		}
+	}
+}
+
+// TestBacklog ensures that the watcher can handle a large backlog of changes
+// in etcd that the client didnt' keep up with, and that whatever final state
+// is available to the client when it actually gets to calling Get().
+func TestBacklog(t *testing.T) {
+	tc := newTestClient(t)
+	defer tc.close()
+
+	k := "test-backlog"
+	value := NewValue(tc.namespaced, k, NoDecoder)
+	watcher := value.Watch()
+	defer watcher.Close()
+
+	tc.put(t, k, "initial")
+	expect(t, watcher, "initial")
+
+	for i := 0; i < 1000; i++ {
+		tc.put(t, k, fmt.Sprintf("val-%d", i))
+	}
+
+	ctx, ctxC := context.WithTimeout(context.Background(), time.Second)
+	defer ctxC()
+	for {
+		valB, err := watcher.Get(ctx)
+		if err != nil {
+			t.Fatalf("Get() returned error before expected final value: %v", err)
+		}
+		val := string(valB.([]byte))
+		if val == "val-999" {
+			break
+		}
+	}
+}